Techniques are disclosed for determining AOA of one or more radar pulses received at a vehicle and originating from a source. The techniques are particularly well-suited to provide pilots with a more accurate determination of the azimuth angle to the radar source, although ground-based and water-based vehicles may benefit as well. Some embodiments discussed herein determine a true estimation of both azimuth and elevation angles, with reference to an aircraft's body-centered coordinate system, to the radar source. These parameters can also be used to determine a more accurate position on the ground for the radar source.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of determining an angle of arrival (AOA) of electromagnetic pulses received at a vehicle and originating from a source, the method comprising: determining a position and orientation of the vehicle within a given dwell time; determining an average initial AOA measurement and an average range from the vehicle to the source, wherein the averages are determined based on a plurality of electromagnetic pulses received within the given dwell time; converting the position of the vehicle into an ECEF Cartesian coordinate system; determining an elevation angle in the NED coordinate system between the vehicle and the source based on the position of the vehicle and the average range; converting the elevation angle from the NED coordinate system into a local body coordinate system centered at the vehicle; determining a position of the source using the ECEF Cartesian coordinate system based on the average initial AOA measurement in the local body coordinate system, the converted elevation angle in the local body coordinate system, and the converted position of the vehicle in the ECEF Cartesian coordinate system; converting the position of the source into the local body coordinate system centered at the vehicle; generating a direction vector from the vehicle to the source in the local body coordinate system; and determining the AOA measurement based on the direction vector, wherein determining the position of the source comprises: determining a possible position of the source for each of a plurality of dwell times; and averaging the possible positions of the source across the plurality of dwell times to determine the position of the source, wherein each of the plurality of dwell times includes an independent number of received electromagnetic pulses.
2. The method of claim 1 , wherein converting the position of the source into the local body coordinate system comprises: converting the position of the source from the ECEF Cartesian coordinate system into a local level coordinate system; and converting the position of the source from the local level coordinate system to the local body coordinate system.
3. The method of claim 1 , wherein determining the position and orientation of the vehicle comprises determining the position and orientation using an inertial navigation system (INS) on board the vehicle.
4. The method of claim 1 , further comprising increasing the range by a given factor and re-determining the elevation angle between the vehicle and the source if the elevation angle is initially determined to be an imaginary number.
5. The method of claim 1 , further comprising increasing the elevation angle by a given amount and re-determining the position of the source if the position of the source is initially determined to yield an imaginary result.
6. The method of claim 1 , wherein determining the average initial AOA measurement comprises determining an average initial AOA measurement of the received plurality of electromagnetic pulses using a plurality of antennas on the vehicle, and wherein determining the average range from the vehicle to the source comprises estimating a range from the vehicle to the source based on a power of each of the received electromagnetic pulses.
7. A system for use on board a vehicle to determine an angle of arrival (AOA) of received electromagnetic pulses from a source, the system comprising: an INS configured to determine a position and orientation of the vehicle; a plurality of antennas arranged around the vehicle and configured to receive an electromagnetic pulse; an amplitude detector configured to determine an amplitude of the received electromagnetic pulse from one or more of the plurality of antennas; and a controller configured to determine an initial AOA measurement of the received electromagnetic pulse based on the measured amplitude of the received electromagnetic pulse, estimate a range from the vehicle to the source based on a power of the received electromagnetic pulse, determine a position and orientation of the vehicle based on one or more reports received from the INS, average the initial AOA measurement and the range from the vehicle to the source over a plurality of received electromagnetic pulses within a given dwell time to determine an average initial AOA measurement and an average range, convert the position of the vehicle into an ECEF Cartesian coordinate system, determine an elevation angle between the vehicle and the source based on the position of the vehicle and the average range, convert the elevation angle into a local body coordinate system centered at the vehicle, determine a position of the source using the ECEF Cartesian coordinate system based on the average initial AOA measurement, the converted elevation angle, and the converted position of the vehicle, convert the position of the source into the local body coordinate system centered at the vehicle, generate a vector from the vehicle to the source in the local body coordinate system, estimating a location of the source over a plurality of dwells and averaging to find a centroid location; calculating a centroid direction vector to the centroid location; and determine the AOA measurement based on the centroid direction vector.
8. The system of claim 7 , wherein the controller is further configured to estimate the range by comparing the power of the received electromagnetic pulse to a table of transmission power values for a plurality of radar systems.
9. The system of claim 7 , further comprising a global positioning system (GPS) configured to determine the position of the vehicle.
10. The system of claim 7 , wherein the controller is configured to convert the position of the source into the local body coordinate system by: converting the position of the source from the ECEF Cartesian coordinate system into a local level coordinate system; and converting the position of the source from the local level coordinate system to the local body coordinate system.
11. The system of claim 7 , wherein the controller is further configured to increase the range by a given factor and re-determine the elevation angle between the vehicle and the source if the elevation angle is initially determined to be an imaginary number.
12. The system of claim 7 , wherein the controller is further configured to increase the elevation angle by a given amount and re-determine the position of the source if the position of the source is initially determined to yield an imaginary result.
13. A computer program product including one or more non-transitory machine-readable mediums having instructions encoded thereon that, when executed by one or more processors, result in a plurality of operations for determining an angle of arrival (AOA) of electromagnetic pulses received at a vehicle and originating from a source, the operations comprising: determining a position and orientation of the vehicle within a given dwell time; determining an average initial AOA measurement and an average range from the vehicle to the source, wherein the averages are determined based on a plurality of electromagnetic pulses received within the given dwell time; converting the average position of the vehicle into an ECEF Cartesian coordinate system; determining an elevation angle between the vehicle and the source based on the position of the vehicle and the average range; converting the elevation angle into a local body coordinate system centered at the vehicle; determining a position of the source using the ECEF Cartesian coordinate system based on the average initial AOA measurement, the converted elevation angle, and the converted position of the vehicle; converting the position of the source into the local body coordinate system centered at the vehicle; generating a vector from the vehicle to the source in the local body coordinate system; and determining the AOA measurement based on the vector, wherein determining the position of the source comprises: determining a possible position of the source for each of a plurality of dwell times; and averaging the possible positions of the source across the plurality of dwell times to determine the position of the source, wherein each of the plurality of dwell times includes an independent number of received electromagnetic pulses.
14. The computer program product of claim 13 , wherein converting the position of the source into the local body coordinate system comprises: converting the position of the source from the ECEF Cartesian coordinate system into a local level coordinate system; and converting the position of the source from the local level coordinate system to the local body coordinate system.
15. The computer program product of claim 13 , wherein determining the position and orientation of the vehicle comprises determining the position and orientation using an inertial navigation system (INS) on board the vehicle.
16. The computer program product of claim 13 , wherein the operations further comprise increasing the range by a given factor and re-determining the elevation angle between the vehicle and the source if the elevation angle is initially determined to be an imaginary number.
17. The computer program product of claim 13 , wherein the operations further comprise increasing the elevation angle by a given amount and re-determining the position of the source if the position of the source is initially determined to yield an imaginary result.
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January 24, 2019
October 5, 2021
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